This invention relates to dry processing, such as dry etching, sputtering, chemical vapor deposition (CVD) or the like, which forms a fine pattern of a semiconductor element or a liquid crystal display element, and more particularly to method of and apparatus for removing foreign particles adhering to a substrate and for cleaning the inside of the apparatus.
Further, this invention relates to a method of an apparatus for cleaning and removing foreign particles from a substrate and cleaning the apparatus in producing elements.
In the production of a semiconductor element or a liquid crystal display element, the element is formed with a fine pattern. Therefore, in forming films, a defect is created on these fine patterns by foreign particles which adhere thereto during an etching process. Due to such defects, a portion of a semiconductor element or a liquid crystal display element will not function and a failure occurs which gives rise to a lowering of the yield.
At present, the source of generating foreign particles is mainly the dry processing device per se, such as a device for dry etching or sputtering, and the reduction in the dust generation by such device per se is a major problem. Further, as for foreign particles which adhere to the substrate, the foreign particles are removed by a wet cleaning process arranged between respective processing steps, thereby preventing defects from being produced. However, in the production of a semiconductor element or a liquid crystal element, there is a desire to enhance the productivity by making the respective processing steps continuous, and therefore, the application of the conventional wet cleaning process becomes difficult. Accordingly, the removing of foreign particles which adhere to a substrate during the dry process steps is an important problem.
A method has been disclosed in Japanese Laid Open Patent publication No. 14713/1991 for reducing dust generation by the processing device per se, wherein foreign particles are prevented from adhering to a substrate by effecting a discharge of the foreign particles flowing in a plasma.
Methods of removing foreign particles which have adhered to a substrate in a dry atmosphere have been disclosed in Japanese Laid Open Patent Publication No. 208217/1988 and Japanese Laid Open Patent Publication No. 1237/1989, wherein, with respect to electrified foreign particles, the foreign particles are separated from the surface of the substrate to which the foreign particles adhere, by blowing an ionized gas, removing the electrification and applying a vibration thereto and the like.
Among the methods of removing foreign particles floating in a plasma, which have been disclosed in the above mentioned publications, it is possible that the foreign particles generated during the plasma processing will not adhere to the substrate. However, foreign particles which have already adhered to the substrate before the plasma processing remain as they were, which is a cause of defects. As is disclosed in the above conventional technique, the foreign particles, which have been generated during the plasma processing, float on a sheath of plasma above the substrate and adhere onto the substrate when the plasma is cut off after the processing is complete. Accordingly, the defects generated in the plasma processing are due to foreign particles which have adhered to the substrate before the plasma processing, and it is a problem in preventing the generation of defects by foreign particles to remove the foreign particles which have adhered to the substrate before the plasma processing.
In these conventional techniques for removing foreign particles that adhere to the substrate in a dry atmosphere, a major adsorbing force for causing the foreign particles to adhere to the substrate is regarded as an electrostatic force produced by electrification. However, an adsorbing force due to van der Waal's force represents a large proportion of the adhering force which produced this problem, and therefore, it is not possible to separate the foreign particles from the substrate simply by removing the electrification. It is a problem in certainly removing the foreign particles to separate the foreign particles from the substrate by overcoming this van der Waal's force.